In known arrangements for turbine diffusers with axial inputs and radial outputs, the fluid is exhausted through a toroidal duct whose axial cross-section is curved and which generally has internal fluid-guiding walls. The diffuser has two functions: firstly to deflect the fluid and secondly to recompress the fluid. Present diffusers have poor aerodynamic qualities due to a recompression gradient on the convex surfaces of the guide walls; this breaks down the fluid flow. Thus, the speed and direction of flow at the output of these diffusers is heterogeneous. This heterogeneous flow of the fluid at the output of the diffuser also greatly hinders proper operation of the downstream connection part whose losses are increased in relation to those in an arrangement where the flow is homogeneous.